ERROR_REQUIRES_RECENT_LOGIN has more precedence than ERROR_EMAIL_ALREADY_IN_USE.
I tried to change the email of the user with another user's email, as a test, and I got ERROR_REQUIRES_RECENT_LOGIN which would take the user to new login process, just later to find out that other email he probably has is already in use. I believe It would be more correct if ERROR_EMAIL_ALREADY_IN_USE had more precedence.